In this video, I'm gonna show you how to diagnose a mass airflow sensor.
Now, what the mass airflow sensor does it actually senses the airflow going into the
engine.
Somewhere between the air filter and the throttle body is where it's going to be mounted, normally
closer to the air filter.
Inside the sensor, those little bars right there is what is sensing the airflow and sometimes
those get dirty, the reason they get dirty is because you're not changing your air filter
soon enough, so make sure you change your air filter regularly.
You can try to clean the sensor with some mass airflow sensor cleaner, hopefully that
works for you but normally if it's gotten to the point where it's dirty enough it probably
needs to be replaced.
Now, we want to check our fuses.
The first thing we do under the hood just take your test light, make sure your test
light works, have this side on the negative.
And we'll go in and test the fuses.
Now, if you can find a wire diagram that works for your vehicle and figure out which fuse
works for the mass airflow sensor then that's the fuse you definitely want to check, but
it's always a good idea to check all the fuses.
You always want to check the connector on the sensor and the wires, you can wiggle test
the wires, make sure they're not loose or anything.
It would be great to have the vehicle running and have a scan tool with a line graph and
wiggle the wires while you're watching that graph and see if you get a spike or anything.
All right with the engine idle, it is idling about 600 RPM right now.
This is what a normal mass airflow sensor looks like on a line graph, it's going up
and down, it's going to fluctuate a little bit but you see it's not fluctuating too much
if you're looking at the numbers.
If you saw a sudden spike, but the engine RPM wasn't moving, then you know that there's
something going on with that mass airflow sensor.
So this is what a bad mass airflow sensor would look like that basically has an open
circuit while the engine is running and it's running about 700 or 800 RPM, and it's not
moving at all, it's just flatlined.
Now, we want to test the power wire on this vehicle, the pink wire is the power wire,
the black and white wire is the ground wire, and the yellow wire is the signal wire.
These are the two wires are for the intake air temp sensor, so we're not worried about
those two.
Now, I don't want to just take my test light and just shove it down in there because I
might end up spreading the terminals and stuff, so I what want to do is just take this little
cover off.
I can get under here.
Slide under here, take this off, then you can access the terminals better and test that
wire.
And that's good, light is on.
You could wiggle the wire you're using the test light right there.
But that's good, we know there's power going to that circuit.
And now we can check the ground circuit which is the black and white wire.
Now you can use an ohmmeter and check the resistance to the ground circuit and just
make sure that it's less than 5 ohms which it is, which is good.
I like to test it with a test light personally, but a meter will work.
When you're testing that you want the other lead of your meter to be attached to a ground.
And then, we're gonna check...go back to DC voltage, we're gonna check the signal wire
that's the yellow wire, the other lead is on the ground.
And just lightly touch that and it's 5 volts, it should be between 4.8 volts and 5.2 volts
which it is, so we're good.
So the next step to test the signal circuit would be is if you had a signal generator,
most people aren't going to have this at home but for the most part we have good power,
we have good ground, and we did have that signal from the PCM.
So generally, this is going to indicate that the mass airflow sensor is bad.
A lot of times though the wiring gets pretty frail internally and could cause an issue,
so pull those wires back and just take a good look at 'em and wiggle them around a lot and
just make sure you don't have a problem there.
And you put this cover back on, put a new mass airflow sensor in, and you're good to
go.
So I hope this video helps you out in understanding how to test a mass airflow sensor circuit.
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